1. Field of the Invention
The present invention relates to a graphics input apparatus for interactively inputting data representing two- or three-dimensional figures of objects into a computer through a personal computer, an interactive Numerical Control (abbreviated NC) system or the like.
2. Description of the Prior Art
A typical example of method for inputting data representing a two-dimensional figure into a computer has heretofore been a "description input process using a predetermined language". This input process comprises a step of describing connections between elements of a two-dimensional figure by using a predetermined language and that of inputting such descriptions into a computer. A typical example of such an input process is APT (Automatically Programmed Tools).
However, this "two-dimensional figure input method using a predetermined language" is disadvantageous in that since the operator has to image a two-dimensional figure to himself and describe the figure by using the predetermined language on the basis of given figures and so forth, the conversion of the three-dimensional figure to the language is very cumbersome.
The present invention is intended to solve the above problem. Therefore, it is an object of the present invention to provide a graphics input apparatus which can recognize a three-dimensional shape intended by the operator simply by receiving a two-dimensional shape handwritten by him.
Furthermore, typical examples of methods for inputting data representing three-dimensional figures into a computer have been heretofore developed are an "input method using primitives" and a "description input method using predetermined (graphics input) language". In the "input method using primitives", a column, a cube and the like are registered as primitives. The primitives are put together by performing a set of operations such as sum, product and difference so as to make a complicated three-dimensional figure. In the description input method using a predetermined language, the relationship among an edge, a node and a plane of three-dimensional figure is described in the predetermined language and inputted into a computer. The three-dimensional graphic data processing are described in various literatures, for example, and article entitled "Study of Three-Dimensional Graphic Processing and Graphic Modeling Technique" (pp. 24-35, published by JOHO SHORI SHINKO JIGYO KYOKAI GIJUTSU CENTER in February, 1983).
However, the input method using primitives is disadvantageous in that since dimensional data is always required for making a figure, it is impossible to input only information on phases of graphic symbols and so on.
The description input method using a predetermined language such as APT makes it possible to input only information on phases of graphic symbols and so on and is fully flexible. However, this method is disadvantageous in that the operator has to image a figure to himself or use given drawings to describe a figure in the predetermined language. In this method, it is cumbersome for the operator to convert the intended three-dimensional figure to the representation in the predetermined language.
The present invention is intended to solve these problems. It is therefore an object of the present invention to provide a graphics input apparatus which enables the operator to input data representing a schematic shape of a three-dimensional form only by causing the operator to hand-write the three-dimensional figure on a two-dimensional screen of a CRT display.